Photovoltaic systems integrated to the grid have received considerable attention around the world. They can be connected to the electrical grid via galvanic isolation (transformer) or without it (transformerless). Despite making galvanic isolation, low frequency transformer increases size, cost and losses. On the other hand, transformerless PV systems increase the leakage current (common-mode c...

In this paper, a differential protection schemes using fuzzy inference system (FIS) for power transformer protection is presented. First we review the concept of differential protection, and illustrate the magnetizing inrush current as they belong to the causes of the protection maloperation. Then relay logic and the algorithm that uses Discreet Fourier transformer for extraction of fundamental...

This paper takes a typical 220 kV three-phase three-limb oil-immersed transformer as an example, this paper building transient field-circuit coupled model and 3D coupled magneto -fluid-thermal model. Considering a nonlinear B–H curve, the magneto model uses the field-circuit coupled finite element method (FEM) to calculate the magnetic flux distribution of the core and the current distribution ...

In the last years controlled switching became an effective method to reduce switching transients which is documented by several publications – especially of CIGRE. Controlled switching is most commonly used for switching capacitor banks. Even though uncontrolled energisation of power transformers can lead to very high inrush current transients whose maximum values can exceed many times the rate...

This project presents reactive power compensation in a distribution power system. DSTATCOM (distribution static compensator) is a reactive power compensator for power quality improvement in a three phase four wire distribution system. A voltage source converter (VSC) based DSTATCOM with a zig-zag transformer is used for the compensation of reactive power for voltage regulation along with load b...

In many text books and papers such as [1]-[5], it is possible to find descriptions about shunt fault calculations and about the influence of the three-phase transformer connection Dyn on the fault currents distribution through distribution transformers. In [6] is described a method for digitally simulating a three-phase power system which is subjected to a fault at one location with blown fuse ...

Abstract—In this paper, the equivalent circuit of the ideal singlephase power transformer with its appropriate voltage current measurement was presented. The calculated values of the voltages and currents of the different connections single phase normal transformer and the results of the simulation process are compared. As it can be seen, the calculated results are the same as the simulated res...

In this paper, a review of PV inverters is reported based on converter characteristics as the number of energy processing stages, the presence of a transformer (high-frequency or 50Hz transformer), and the adopted configuration of the PV field. In particular, the considered solutions have been evaluated depending on efficiency, input current ripple and life-time of the capacitors coupling with ...

Several precise laboratory methods are now available for the determination of the ratio and phase angle of current transformers. 1 These, however, all require a considerable amount of special apparatus, such as carefully calibrated noninductive shunts and very sensitive alternating-current detectors, and are therefore not suited for use under shop or central-station conditions. The task of comp...

This paper presents the design and analysis and of the proposed zero voltage zero current switching (ZVZCS) full bridge dc-dc converter with transformer isolation and current doubler rectifier for high power and high performance by introducing ZVS for lagging leg and ZCS for leading leg operation It has a simple and robust structure with asymmetrical shifted pulse width modulation technique. Th...